The need to remove grit from wastewater is a well-known concern. The grit takes the form of minute particles that, if not removed, interferes with the performance of downstream machinery where the grit may collect. In particular, the grit may lead to premature failure of components, accelerated wear, etc. The industry has used various arrangements over the years to remove as much grit as possible from wastewater at its initial introduction to a treatment facility. Depending on local conditions, the grit may vary in size (as well as composition), ranging from coarse grit on the order of about 300 microns down to fine grit typically on the order of about 100 microns.
Of the various types of grit removal systems, one exemplary type is a vortex-based configuration, where the influent is introduced in a tangential direction around the top periphery of a funnel-like element (referred to hereinafter as a “frusto-conical tray”, or simply “tray”). The vortex created by the circulating fluid causes the grit particulate to be directed to the sides of the tray, with the grit-free fluid spun outward and away from funnel. U.S. Pat. No. 6,881,350 issued to G. E. Wilson illustrates an exemplary vortex type of grit removal system, using a stacked set of frusto-conical trays, with the influent introduced in parallel to the vertical stack of trays, thus increasing the volume of fluid that is treated within a given space. While able to increase the number of trays used to remove grit, the pressure differential at the input to the various trays is problematic and results in non-uniform grit removal. U.S. Pat. No. 6,852,239 issued to G. E. Wilson describes an improved type of feed configuration for use in this tray-type of grit removal system, where the geometry of the inlet duct is modified to reduce headloss (where headloss is defined as the difference in pressure between two points in a hydraulic system, here as a result of elevation changes). The inlet duct described in the '239 patent is also formed to have a set of separate output nozzles, each vertically oriented and coupled to a separate tray.
While the modified inlet duct geometry may reduce the overall headloss, the vertical arrangement of the inlet duct results in uneven path lengths between the entrance of the system and each tray, presenting a varying pressure differential to each tray. As a result, short-circuiting of flow and grit loadings to each tray will occur.